1. Field of the Invention
The present invention relates to a semiconductor memory module, and more particularly to a semiconductor memory module with a reverse mounted chip resistor, and a method of fabricating the same.
2. Description of the Related Art
Semiconductor memory modules include not only semiconductor memory chips, but also passive devices such as capacitors and resistors, which are all generally mounted on a module substrate. Generally, the resistor of a memory module is mounted in the form of a chip resistor beside an external connection port of a module substrate. The chip resistor helps control the current within the circuit and typically drops the voltage.
FIG. 1 illustrates the structure of a typical chip resistor. The chip resistor includes a thin-film resistive material 2, such as TaN or RuO2, on an insulating substrate 1 composed of a material such as alumina. A thin-film internal electrode 3 contacts both ends of the resistive material 2 and a plated electrode 4 is formed on the internal electrode 3. A protection layer 5, such as a glass layer, is formed over the resistive material 2 to protect the resistive material 2.
Because of substantially similar ends of the chip resistor, which are used when mounting the chip resistor to the module substrate, the chip resistor may be mounted with either the surface with the resistive material facing upward, or the surface with the protective layer 5.
However, when the resistive material faces upward the resistive material is exposed and both the resistive material and the electrode are susceptible to physical damage during assembly or handling by a user. Accordingly, the electrode can peel off or the resistive material can break, causing an open circuit. Moreover, when a mounting facility grips the chip resistor with a vacuum nozzle to place the chip resistor onto the module substrate, the vacuum nozzle must grip the uneven surface of the resistive material and the protection layer, which can cause pickup errors and misalignment.
These problems may be partially solved when the resistive material faces downward during mounting. However, even in this case, the chip resistor may be slanted because the resistive material and protection layer are higher than the plated electrodes.